[CodeGen] Use getCharWidth() more consistently in CGRecordLowering. NFC

[bjope]

Summary

When using getByteArrayType the requested size is calculated in
char units, but the type used for the array was hardcoded to the
Int8Ty. This patch is using getCharWIdth a bit more consistently
by using getIntNTy in combination with getCharWidth, instead
of explictly using getInt8Ty.

[rjmccall]

LGTM

clang/lib/CodeGen/CGRecordLayoutBuilder.cpp

struct CGRecordLowering {
   ///
   /// Note specifically that the ms_struct attribute doesn't change this.
   bool isOverlappingVBaseABI() {
     return !Context.getTargetInfo().getCXXABI().isMicrosoft();
   }
 
   /// Wraps llvm::Type::getIntNTy with some implicit arguments.
   llvm::Type *getIntNType(uint64_t NumBits) {
+    unsigned AlignedBits = llvm::alignTo(NumBits, Context.getCharWidth());
+    return llvm::Type::getIntNTy(Types.getLLVMContext(), AlignedBits);
+  }
+  /// Get the LLVM type sized as one character unit.
+  llvm::Type *getCharType() {
     return llvm::Type::getIntNTy(Types.getLLVMContext(),
-                                 (unsigned)llvm::alignTo(NumBits, 8));
+                                 Context.getCharWidth());
   }
-  /// Gets an llvm type of size NumBytes and alignment 1.
-  llvm::Type *getByteArrayType(CharUnits NumBytes) {
-    assert(!NumBytes.isZero() && "Empty byte arrays aren't allowed.");
-    llvm::Type *Type = llvm::Type::getInt8Ty(Types.getLLVMContext());
-    return NumBytes == CharUnits::One() ? Type :
-        (llvm::Type *)llvm::ArrayType::get(Type, NumBytes.getQuantity());
+  /// Gets an llvm type of size NumChars and alignment 1.
+  llvm::Type *getByteArrayType(CharUnits NumChars) {
+    assert(!NumChars.isZero() && "Empty byte arrays aren't allowed.");
+    llvm::Type *Type = getCharType();
+    return NumChars == CharUnits::One() ? Type :
+        (llvm::Type *)llvm::ArrayType::get(Type, NumChars.getQuantity());
   }
   /// Gets the storage type for a field decl and handles storage
   /// for itanium bitfields that are smaller than their declared type.
   llvm::Type *getStorageType(const FieldDecl *FD) {
     llvm::Type *Type = Types.ConvertTypeForMem(FD->getType());
     if (!FD->isBitField()) return Type;
     if (isDiscreteBitFieldABI()) return Type;
     return getIntNType(std::min(FD->getBitWidthValue(Context),